U.S. patent number 8,007,645 [Application Number 11/993,782] was granted by the patent office on 2011-08-30 for biosensor.
This patent grant is currently assigned to Panasonic Corporation. Invention is credited to Akihisa Higashihara, Hiroyuki Tokunaga, Eriko Yamanishi.
United States Patent |
8,007,645 |
Yamanishi , et al. |
August 30, 2011 |
Biosensor
Abstract
A biosensor can supply a sample solution accurately and easily,
and includes a capillary for collecting a sample solution and
analyzes a specific substance in the sample solution, an air hole,
and at least two supply ports, i.e., a sample supply port and an
auxiliary sample supply port, so that supply of the sample solution
can be performed from either of the supply ports. Even when the
sample supply port is closed up with a fingertip or the like and
supply of the sample solution is stopped, the sample solution can
be quickly supplied from the other auxiliary sample supply
port.
Inventors: |
Yamanishi; Eriko (Ehime,
JP), Tokunaga; Hiroyuki (Ehime, JP),
Higashihara; Akihisa (Ehime, JP) |
Assignee: |
Panasonic Corporation (Osaka,
JP)
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Family
ID: |
37570566 |
Appl.
No.: |
11/993,782 |
Filed: |
June 23, 2006 |
PCT
Filed: |
June 23, 2006 |
PCT No.: |
PCT/JP2006/312665 |
371(c)(1),(2),(4) Date: |
December 21, 2007 |
PCT
Pub. No.: |
WO2006/137549 |
PCT
Pub. Date: |
December 28, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20100078322 A1 |
Apr 1, 2010 |
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Foreign Application Priority Data
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Jun 24, 2005 [JP] |
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2005-184306 |
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Current U.S.
Class: |
204/403.04;
204/403.01; 204/403.14; 204/403.11 |
Current CPC
Class: |
G01N
27/3272 (20130101) |
Current International
Class: |
G01N
27/327 (20060101); G01N 27/26 (20060101) |
Field of
Search: |
;204/435,400-403.15,406,407 ;600/345-365 ;435/4,14,25,287.1
;436/43,44,68,95 ;205/775,786.5,787,792,777.5,778
;422/401,402,408,412,419 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2 002-168821 |
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Jun 2002 |
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JP |
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2003-116821 |
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Apr 2003 |
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JP |
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2005-43122 |
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Feb 2005 |
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JP |
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Other References
International Search Report issued Jul. 25, 2006 in the
International (PCT) Application No. PCT/JP2006/312665. cited by
other .
Written Opinion of the ISA issued Jul. 25, 2005 in the
International (PCT) Application No. PCT/JP2006/312665. cited by
other.
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Primary Examiner: Barton; Jeffrey T.
Assistant Examiner: Dieterle; Jennifer
Attorney, Agent or Firm: Wenderoth, Lind & Ponack,
L.L.P.
Claims
The invention claimed is:
1. A biosensor comprising: a first insulating substrate and a
second insulating substrate bonded together; a sample supply port
which opens at one end of the bonded insulating substrates, and to
which a sample solution is applied; a capillary communicated with
the sample supply port, and into which the applied sample solution
is introduced; and an air hole which is positioned at an end of the
capillary opposite the sample supply port and communicated with air
inside the capillary, wherein said sample supply port and said
capillary are formed by bonding the insulating substrates together,
wherein an auxiliary sample supply port communicated with said
capillary, through which the applied sample solution is introduced
into the capillary, is formed in one of the first insulating
substrate and the second insulating substrate and provided in the
vicinity of said sample supply port, wherein said auxiliary sample
supply port is a through-hole penetrating said one of the
insulating substrates and is in fluid communication with outer air
between the auxiliary sample supply port and the sample supply
port, and wherein an entirety of the capillary between the
auxiliary sample supply port and the air hole is covered by said
one of the first insulating substrate and the second insulating
substrate.
2. A biosensor as defined in claim 1, wherein a total aperture area
of said auxiliary sample supply port is 0.01 mm.sup.2 to 3
mm.sup.2.
3. A biosensor as defined in claim 1, wherein a distance between
said sample supply port and said auxiliary sample supply port is
0.05 to 5 mm.
4. A biosensor as defined in claim 1, wherein a surface-activating
treatment is applied to at least a portion of a surface of the
first insulating substrate or the second insulating substrate, said
portion facing the capillary.
5. A biosensor as defined in claim 1, wherein a surface-activating
treatment is applied to an inner wall of the auxiliary sample
supply port.
6. A biosensor as defined in claim 1, wherein said auxiliary supply
port is a first auxiliary supply port, and the biosensor comprises
at least one additional auxiliary supply port, and wherein a total
aperture area of the auxiliary sample supply ports is 0.01 mm.sup.2
to 3 mm.sup.2.
7. A biosensor as defined in claim 1, wherein said auxiliary sample
supply port is disposed between said air hole and said sample
supply port.
8. A biosensor as defined in claim 1, wherein said auxiliary supply
port is a first auxiliary supply port and the biosensor includes at
least one additional auxiliary supply port, and wherein each of
said auxiliary sample supply ports is disposed between said air
hole and said sample supply port.
9. A biosensor as defined in claim 1, wherein said auxiliary sample
supply port and said air hole are disposed in said second
insulating substrate, and wherein said auxiliary sample supply port
is disposed between said air hole and said sample supply port.
10. A biosensor as defined in claim 1, wherein said sample supply
port is formed between said insulating substrates, and said air
hole is formed in one of said insulating substrates.
11. A biosensor as defined in claim 1, wherein a total aperture
area of said auxiliary sample supply port is 0.01 mm.sup.2 to 3
mm.sup.2, and wherein a distance between said sample supply port
and said auxiliary sample supply port is 0.05 to 5 mm.
12. A biosensor as defined in claim 1, wherein the entirety of the
capillary between the auxiliary sample supply port and the air hole
is covered and enclosed between the first insulating substrate and
the second insulating substrate.
13. A biosensor as defined in claim 1, wherein said auxiliary
sample supply port is spaced apart from the sample supply port such
that a portion of said one of the first insulating substrate and
the second insulating substrate is disposed between the auxiliary
sample supply portion and the sample supply port.
14. A biosensor as defined in claim 13, wherein said auxiliary
sample supply port is a first auxiliary supply port formed in the
first insulating substrate, and a second auxiliary supply port is
formed in the second insulating substrate.
15. A biosensor as defined in claim 13, wherein said through-hole
for the auxiliary sample supply port is fabricated using a
laser.
16. A biosensor as defined in claim 1, wherein electrodes and a
reagent layer for electrochemically analyzing a specific substance
in the sample solution are provided on a surface of the first
insulating substrate or the second insulating substrate, said
surface facing the capillary.
17. A biosensor as defined in claim 16, wherein the first
insulating substrate and the second insulating substrate have
different shapes at an end of the biosensor where the sample supply
port is formed.
18. A biosensor as defined in claim 17, wherein the electrodes and
the reagent layer are provided on the first insulating substrate,
and the auxiliary sample supply port is provided in the first
insulating substrate.
Description
TECHNICAL FIELD
The present invention relates to a biosensor for analyzing a
specific component in a sample solution, and more particularly, to
a biosensor which collects a small amount of sample solution by
capillary phenomenon onto a small-size test specimen, and analyzes
the sample solution.
BACKGROUND ART
A biosensor is a sensor for determining a quantity of a base
substance in a sample solution, which utilizes a molecule
recognizing ability of a biological material such as
micro-organism, enzyme, antibody, DNA, RNA or the like to employ
the biological material as a molecule discrimination element. To be
specific, the biosensor determines a quantity of a base substance
contained in a sample solution by utilizing a reaction which occurs
when a biological material recognizes an objective substrate, such
as consumption of oxygen due to respiration of a micro-organism,
enzyme reaction, light emission, and the like. Among various kinds
of biosensors, an enzyme sensor has come into practical use. For
example, an enzyme sensor as a biosensor for glucose, lactic acid,
cholesterol, or amino acid has been utilized for medical analysis
and food industry. In this enzyme sensor, an electron carrier is
reduced by electrons that are generated due to a reaction between a
base substance included in a sample solution as an analyte and
enzyme or the like, and a measurement unit electrochemically
measures a reduction quantity of the electron carrier, thereby
performing quantitative analysis for the sample.
There have been proposed various types of biosensors. For example,
as a biosensor that facilitates measurement of a blood glucose
level, there is a biosensor comprising a first insulating substrate
on which a pair of electrodes and a reagent layer are formed, a
second insulating substrate bonded to the first insulating
substrate via a spacer, and a capillary for collecting a sample
solution, which is provided between the both insulating substrates.
The biosensor is constituted such that blood obtained by puncturing
the human body is introduced by capillary phenomenon into the
capillary from a sample supply port that opens at one ends of the
both substrates.
In this biosensor, however, there is a possibility that the blood
is not successfully introduced into the capillary depending on the
angle of the biosensor when the blood is applied onto the sample
supply port, and thereby the blood might be attached to the outer
surface of the insulating substrate by mistake. In this case, even
when the user tries to supply the blood again, the blood attached
to the outer surface impedes the user from successfully supplying
the blood into the capillary, resulting in faulty measurement and
measurement errors.
In order to solve this problem, the inventors of the present
invention have proposed a biosensor in which the ends of the both
substrates which constitute the sample supply port are formed in
different shapes when viewed planarly so that blood can always be
introduced into the capillary successfully without being influenced
by the angle of the biosensor when the blood is applied (refer to
Patent Document 1).
FIG. 8 illustrates an exploded perspective view and a
cross-sectional view of the biosensor disclosed in Patent Document
1. In FIG. 8, reference numeral 1 denotes a first insulating
substrate, and a measurement electrode 2, a counter electrode 3,
and a detector electrode 4, which comprise an electric conducting
material, are formed on the first insulating substrate 1.
The conventional biosensor 800 is formed by bonding the first
insulating substrate 1, a spacer 6, and a second insulating
substrate 8 together, and a capillary 7 is formed by the existence
of a notch in the spacer 6. A test sample is introduced into the
capillary 7 from its front end by a sample supply port 13 that is
formed by the bonding and an air hole 9 formed through the
insulating substrate 1.
Further, the measurement electrode 2, the counter electrode 3, and
the detector electrode 4 which are formed on the first insulating
substrate 1 are exposed in the capillary 7, and a reagent layer 5
is formed in a position opposed to these electrodes.
A measurement instrument (not shown) having terminals to be
connected to leads 10, 11, and 12 of the electrodes is inserted in
the biosensor before introduction of blood, and variation in the
electric characteristics which occurs due to a reaction of the
blood with the reagent is detected between the measurement
electrode 2 and the counter electrode 3 after introduction of
blood, thereby measuring a glucose concentration. Patent Document
1: Japanese Published Patent Application No. 2002-168821).
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
In blood glucose measurement in recent years, it is desired to
minimize the quantity of blood to be collected in order to reduce
pain of diabetic patient as much as possible. Therefore,
development of a biosensor in which the size of the capillary for
collecting blood and the size of the sample supply port are further
reduced has been progressed.
However, such miniaturization in the conventional biosensor has
caused a problem that the sample supply port is easily closed up
when a deformable object such as a finger chip is pressed
thereto.
FIG. 9 shows a state where blood is aspirated in the conventional
biosensor.
As shown in FIG. 9(a), when the sample supply port 13 is closed up
by a fingertip, supply of blood is interrupted, and the blood is
not completely filled in the capillary 7 but stops in the middle of
the capillary 7. Then, shortage of sample quantity occurs, which
may prevent measurement, or display of incorrect results. Further,
even when the capillary is completely filled with the blood by
rightly separating the finger as shown in FIG. 9(b) after the
finger has once closed the sample supply port 13, there occurs a
difference in dissolution of the reagent layer due to the initially
introduced blood, resulting in variations in measurement, and
therefore, accurate measurement cannot be carried out.
Although it might be considered that the difference in the shapes
between the first insulating substrate and the second insulating
substrate may be further increased to prevent the fingertip from
closing the sample supply port, this is a distant idea. The reason
is as follows. If the difference in the shapes is increased too
much, not only the blood stored inside the capillary but also the
blood stored outside the capillary increases, and thus more blood
is required.
The present invention is made to solve the above-described problems
and has for its object to provide a biosensor having a construction
that can reliably collect a sample solution into a capillary even
when the quantity of the sample solution is very small.
Measures to Solve the Problems
In order to solve the above-mentioned problems, there is provided a
biosensor which is formed by bonding a first insulating substrate
and a second insulating substrate together, and comprises a sample
supply port which opens at one end of the both substrates, to which
a sample solution is applied, a capillary communicated with the
sample supply port, into which the applied sample solution is
introduced by capillary phenomenon, and an air hole which is
positioned at an end of the capillary and communicated with air
inside the capillary, the supply port, the capillary, and the air
hole being formed by the bonding of the both insulating substrates,
wherein at least one auxiliary sample supply port communicated with
the capillary, through which the applied sample solution is
introduced into the capillary, is provided in the vicinity of the
sample supply port.
Further, the auxiliary sample supply port is obtained by forming a
through-hole in the first insulating substrate or the second
insulating substrate so as to leave a portion of the insulating
substrate between the auxiliary sample supply portion and the
sample supply port.
Further, a spacer having a groove to provide the sample supply
port, the auxiliary sample supply port, and the capillary is
disposed between the first insulating substrate and the second
insulating substrate, and the auxiliary sample supply port is
provided at the ends of the both substrates.
Effects of the Invention
According to the present invention, since a biosensor which has a
capillary structure and performs measurement with a very small
quantity of sample is constituted as described above, even when a
sample supply port is closed up by elastic skin such as fingertip,
brachial region, or abdominal region of a test subject, it is
possible to perform reliable aspiration of the sample solution from
an auxiliary sample supply port into the capillary.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates an exploded perspective view and a
cross-sectional view of a biosensor 100 according to a first
embodiment of the present invention.
FIG. 2 illustrates an exploded perspective view and a
cross-sectional view of a biosensor 200 according to a modification
of the first embodiment.
FIG. 3 illustrates an exploded perspective view and a
cross-sectional view of a biosensor 300 according to another
modification of the first embodiment.
FIG. 4 illustrates an exploded perspective view and a
cross-sectional view of a biosensor 400 according to still another
modification of the first embodiment.
FIG. 5 illustrates an exploded perspective view and a
cross-sectional view of a biosensor 500 according to a second
embodiment of the present invention.
FIG. 6 illustrates an exploded perspective view and a
cross-sectional view of a biosensor 600 according to a third
embodiment of the present invention.
FIG. 7 illustrates an exploded perspective view and a
cross-sectional view of a biosensor 700 according to a comparison
example of the present invention.
FIG. 8 illustrates an exploded perspective view and a
cross-sectional view of the conventional biosensor 800.
FIG. 9 is a cross-sectional view illustrating a state where blood
is aspirated in the conventional biosensor 800.
FIG. 10 is a cross-sectional view illustrating a state where blood
is aspirated in the biosensor 100 according to the first
embodiment.
DESCRIPTION OF THE REFERENCE NUMERALS
100 . . . biosensor 200 . . . biosensor 300 . . . biosensor 400 . .
. biosensor 500 . . . biosensor 600 . . . biosensor 700 . . .
biosensor 800 . . . biosensor 1 . . . first insulating substrate 2
. . . measurement electrode 3 . . . counter electrode 4 . . .
detector electrode 5 . . . reagent layer 6 . . . spacer 7 . . .
capillary 8 . . . second insulating substrate 9 . . . air hole 10 .
. . lead 11 . . . lead 12 . . . lead 13 . . . sample supply port 14
. . . auxiliary sample supply port 15 . . . notch 16 . . . blood 17
. . . fingertip
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a biosensor according to the present
invention will be described taking a blood glucose sensor as an
example with reference to the drawings.
Embodiment 1
FIG. 1 illustrates an exploded perspective view and a
cross-sectional view of a biosensor 100 according to a first
embodiment of the present invention.
In the biosensor 100 shown in FIG. 1, reference numeral 1 denotes a
first insulating substrate having a portion near a front end being
formed approximately in a semicircular shape, and a portion that
follows the front end to reach an a rear end being formed in a
rectangle. A measurement element 2, a counter electrode 3, and a
detector electrode 4 which are composed of an electric conducting
material are formed on the first insulating substrate 1. Reference
numeral 8 denotes a second insulating substrate which is formed in
a shape similar to that of the first insulating substrate 1,
reference numeral 6 denotes a spacer which is disposed between the
first insulating substrate 1 and the second insulating substrate 8
and is formed in a shape similar to those of the both insulating
substrates, and reference numeral 7 denotes a capillary which is
formed so as to form an approximately rectangle convex portion in
the vicinity of the front end of the spacer, along the longitudinal
direction of the spacer.
The biosensor 100 is formed by bonding the first insulating
substrate 1, the spacer 6, and the second insulating substrate 8
together, and the capillary 7 is formed by existence of the
above-mentioned notch in the spacer 6. A test sample is introduced
into the capillary 7 by a sample supply port 13 that is formed by
the bonding, and an air hole 9 that is provided through the first
insulating substrate 1 in a position opposed to a rear end of the
capillary 7.
Further, reference numerals 10, 11, and 12 denote leads of the
measurement electrode 2, the counter electrode 3, and the detector
electrode 4, respectively, which correspond to the rear end
portions of the respective electrodes disposed on the first
insulating substrate 1, and reference numeral 13 denotes a sample
supply port which is formed by that a forward space portion of the
capillary 7 is sandwiched by the first and second insulating
substrates 1 and 8.
Further, the measurement electrode 2, the counter electrode 3, and
the detector electrode 4 formed on the first insulating substrate 1
are exposed in the capillary 7, and a reagent layer 5 is disposed
in a position opposed to these electrodes.
When performing measurement using the biosensor 100 of the first
embodiment, variations in the electric characteristics between the
measurement electrode 2 and the counter electrode 3 are detected
with the biosensor 100 being inserted in a measurement instrument
(not shown) having terminals which are to be connected to the leads
10, 11, and 12 of the respective electrodes 2, 3, and 4, thereby to
analyze the characteristics of the test sample.
While the detector electrode 4 functions as an electrode for
detecting a shortage in the quantity of the sample, it may be used
as a reference electrode or a portion of the counter electrode.
While in FIG. 1 the respective electrodes 2, 3, and 4 are disposed
on the first insulating substrate 1, these electrodes may be
partially disposed on the opposed second insulating substrate 8 as
well as on the first insulating substrate 1.
Preferable materials of the first insulating substrate 1, the
spacer 6, and the second insulating substrate 8 include
polyethylene terephthalate, polycarbonate, and polyimide. The
thicknesses of the first and second insulating substrates are
desired to be 0.1 to 5.0 mm.
Further, the electric conducting material constituting the
respective electrodes 2, 3, and 4 may include a single substance
such as a noble metal (gold, platinum, or palladium) or carbon, or
a complex substrate such as carbon paste or a noble metal paste.
Sputtering or the like is adopted for the former substance while
screen printing or the like is adopted for the latter substance,
thereby easily forming the electric conducting layer on the first
insulating substrate 1 or the second insulating substrate 8.
Further, when forming the respective electrodes, initially an
electric conducting layer is formed on the entire surface or a
portion of the first insulating substrate 1 or the second
insulating substrate 8 by the above-mentioned sputtering or screen
printing, and then slits are formed in the electric conducting
layer using a laser or the like, thereby fabricating the separated
electrodes. Alternatively, the respective electrodes can be
similarly produced by screen printing or sputtering using a print
board or a mask board on which electrode patterns have already been
formed.
The reagent layer 5 including enzyme, electron carrier, hydrophilic
macromolecule, and the like is formed on the electrodes 2, 3, and
4. The enzyme may be any of glucose oxidase, lactate oxidase,
cholesterol oxidase, cholesterol esterase, uricase, ascorbate
oxidase, bilirubin oxidase, glucose dehydrogenase, and lactate
dehydrogenase. The electron carrier may be any of potassium
ferricyanide, p-benzoquinone and its derivative, phenazine
methosulfate, methylene blue, and ferrocene and its derivative.
The hydrophilic macromolecule may be any of carboxymethyl
cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl
cellulose, ethyl cellulose, ethylhydroxyethyl cellulose,
carboxymethylethyl cellulose, polyvinyl alcohol,
polyvinylpyrrolidone, polyamino acid such as polylysine,
polystyrene sulfonate, gelatine and its derivative, acrylic acid
and its salt, and agarose gel and its derivative.
Next, the capillary 7 to which blood is to be supplied is formed by
bonding the first insulating substrate 1 and the second insulating
substrate 8 with the spacer 6 between them. The sample supply port
13 through which the blood is to be introduced into the capillary 7
is opened at the ends of the first insulating substrate 1 and the
second insulating substrate 8.
In this first embodiment, the thickness of the spacer 6 is 0.025 to
0.5 mm, the width of the capillary 7 is 0.1 to 10 mm, and the
volume of the capillary 7 is 0.1 to 5 .mu.L.
The construction of the first embodiment is characterized by that
an auxiliary sample supply port 14 penetrating through the second
insulating substrate 8 on the capillary 7 is provided. After this
auxiliary sample supply port 14 is formed through the second
insulating substrate 8, the second insulating substrate 8 is bonded
to the first insulating substrate 1 and the spacer 6, thereby
completing the biosensor.
Since the auxiliary sample supply port 14 is provided, even when
the sample supply port 13 is closed up with a finger chip when
applying the blood and thereby supply of the blood from the sample
supply port 13 is blocked, the blood can be introduced into the
capillary from the auxiliary sample supply port 14 provided through
the second insulating substrate 8 as shown in FIG. 10, whereby the
capillary 7 can be completely filled with the blood.
This auxiliary sample supply port 14 is desired to be provided in a
position to which the sample solution is always attached when the
sample solution is supplied. Hereinafter, a description will be
given of the position, size, shape, and number of the auxiliary
sample supply port 14.
The distance between the sample supply port 13 and the auxiliary
sample supply port 14, i.e., the size of A shown in the
cross-sectional view of FIG. 1(b), is desirably at least 0.05 to
5.0 mm. When the distance is smaller than 0.05 mm, there is a
possibility that the two supply ports might be connected and the
effect as the auxiliary sample supply port is reduced. Further, in
the recent biosensor which is desired to minimize the quantity of
blood, if the distance is larger than 5.0 mm, it becomes difficult
to apply the sample to the sample supply port 13 and to the
auxiliary sample supply port 14 simultaneously.
The area of the auxiliary sample supply port 14 is desired to be
0.01 to 3.0 mm.sup.2. When the area is smaller than 0.01 mm.sup.2,
the auxiliary sample supply port 14 lacks the ability of aspirating
the sample solution, and thereby the supply speed is reduced or the
supply is stopped halfway. When the area is larger than 3.0
mm.sup.2, the size of the capillary must be increased, which leads
to an increase in the quantity of the sample, and therefore, this
is a distant idea.
It is desired to process the auxiliary sample supply port 14 using
a laser. Although press cutting, die cutting, and Thomson cutting
are also applicable for processing the supply port, laser
processing is most preferable because it enables
microfabrication.
A plurality of auxiliary sample supply ports 14 may be provided on
the second insulating substrate 8, with favorable effects. Further,
the shape of the auxiliary sample supply port 14 is not restricted
to that mentioned above so long as the above-mentioned conditions
are satisfied. For example, it may be circular, oval, linear,
rectangular, triangular, or the like.
Further, while the auxiliary sample supply port 14 is provided on
the second insulating substrate 8, it may be provided on the first
insulating substrate 1. At this time, the position, shape, and size
of the auxiliary sample supply port 14 are identical to those
mentioned above.
Further, the shape of the biosensor 100 is not restricted to that
of the first embodiment shown in FIG. 1, and the same effects as
mentioned above can be achieved even when the biosensor has a shape
according to a modification shown in FIG. 2 or a shape according to
another modification shown in FIG. 3.
To be specific, a biosensor 200 according to a modification of the
first embodiment shown in FIG. 2 has plural auxiliary sample supply
ports 14a and 14b.
Further, a biosensor 300 according to another modification of the
first embodiment shown in FIG. 3 has a rectangular auxiliary sample
supply port 14.
Furthermore, FIG. 4 shows a biosensor 400 according to still
another modification of the first embodiment. This biosensor 400 is
constituted such that the first insulating substrate 1 and the
second insulating substrate 8 which form the capillary 7 are bonded
together shifted from each other so that the end portions thereof
viewed planarly are located in different positions.
That is, in FIG. 4, the second insulating substrate 8 and the
spacer 6 are protruded by 0.1 to 1.0 mm toward the sample supply
port 13 with respect to the first insulating substrate 1.
The biosensors 200, 300, and 400 shown in FIGS. 2, 3, and 4 also
achieve the same effects as the biosensor 100 shown in FIG. 1.
When the electrodes 2, 3, and 4 and the reagent layer 5 for
electrochemically analyzing a specific substance in the sample
solution are provided inside the capillary 7, it is desired that
these electrodes 2, 3, 4 and the reagent layer 5 are not disposed
at a position on the first insulating substrate 1 directly beneath
the auxiliary sample supply port 14.
If the auxiliary sample supply port 14 is disposed above the
electrodes 2, 3, and 4, the sample solution on the electrodes is
likely to vary, and this variation may cause undesirable variation
in the response value.
The biosensors 200, 300, and 400 shown in FIGS. 2, 3, and 4 also
achieve the same effects as the biosensor 100 shown in FIG. 1.
Further, in the above-mentioned biosensors 100, 200, 300, and 400,
it is desired that a surface-activating treatment is applied to the
entirety or a portion of the inner wall of the capillary 7.
Thereby, even when the area of the sample supply port is small, the
capillary can speedily aspirate the sample solution.
Further, it is desired that a surface-activating treatment is
applied to the inner side of the auxiliary sample supply port 14,
or the entire inner wall of the capillary, or a portion of the
inner wall of the capillary in the vicinity of the auxiliary sample
supply port.
When a surface-activating treatment is applied to the inner side of
the auxiliary sample supply port 14 or the inner wall of the
capillary, aspiration of the sample solution is quickly started as
soon as the sample solution contacts the auxiliary sample supply
port 14, and thereby the capillary is filled with the sample
solution before the supply port is closed up by a fingertip or the
like.
The surface-activating treatment includes coating of a nonionic,
cationic, anionic, or zwitterionic surfactant, corona discharge
treatment, and physical processing to form fine concavities and
convexities on the surface.
As described above, according to the biosensor of the first
embodiment, even when the sample supply port 13 is closed up while
the sample solution is being supplied, the sample solution is
speedily supplied from the auxiliary sample supply port 14, and
thereby the sample solution is aspirated into the capillary
accurately and easily.
Embodiment 2
FIG. 5 illustrates an exploded perspective view and a
cross-sectional view of a biosensor 500 according to a second
embodiment of the present invention.
In the biosensor 500 of the second embodiment shown in FIG. 5,
auxiliary sample supply ports 14 are provided on both the first
insulating substrate 1 and the second insulating substrate 8.
Since the auxiliary sample supply ports 14 are provided on the two
insulating substrates 1 and 8, respectively, even if the sample is
applied from a biased angle, the sample can be reliably aspirated
into the space 6.
Further, as described in the first embodiment, plural auxiliary
sample supply ports 14 may be provided on the respective substrates
with the same effects as mentioned above.
Further, the shape of the auxiliary sample supply port 14 is not
particularly restricted, and it may be circular, oval, linear,
rectangular, or triangular.
Embodiment 3
FIG. 6 illustrates an exploded perspective view and a
cross-sectional view of a biosensor 600 according to a third
embodiment of the present invention.
In the biosensor 600 of the third embodiment shown in FIG. 6, the
capillary 7 branches in a Y shape in the vicinity of the front end,
and one of the branches serves as the sample supply port 13 while
the other serves as the auxiliary sample supply port 14.
In this third embodiment, since the spacer 6 is provided with the
two sample supply ports, the same effects as those of the first and
second embodiments are achieved. Further, since the sample supply
port 13 and the auxiliary sample supply port 14 can be
simultaneously patterned in the spacer 6, the number of process
steps in the sensor fabrication can be reduced.
Hereinafter, a specific example of the present invention will be
described in detail.
A biosensor constituted as mentioned below is used as an
example.
After a palladium thin film having a thickness of about 8 nm is
formed by sputtering over the entire surface of a first insulating
substrate comprising polyethylene terephthalate, slits are
partially formed in the thin film by using a YAG laser, thereby
separately forming a measurement electrode, a counter electrode,
and a detector electrode.
Thereafter, an aqueous solution containing glucose dehydrogenase as
an enzyme and potassium ferricyanide as an electron carrier is
dropped circularly so as to partially cover the counter electrode
and the detector electrode with the measurement electrode being in
the center, and then dried, thereby forming a reagent layer.
Further, a spacer comprising polyethylene terephthalate and a
second insulating substrate also comprising polyethylene
terephthalate are bonded onto the first insulating substrate.
A surface-activating treatment is previously applied to the surface
of the second insulating substrate on the sample supply port side,
and an air hole is formed through the second insulating substrate,
and further, an auxiliary sample supply port is formed at a
position apart by 0.2 mm from the sample supply port.
The above-mentioned members are bonded together to complete a
biosensor having a capillary into which blood is introduced, which
has the same construction as that shown in FIG. 1.
In order to confirm the effects of the present invention, there are
fabricated fourteen types of sensors as follows:
a conventional biosensor 800 shown in FIG. 8 ((1));
biosensors 100 according to the first embodiment shown in FIG. 1,
wherein the aperture areas of the auxiliary sample supply ports 14
are 0.005 mm.sup.2, 0.010 mm.sup.2, 0.030 mm.sup.2, and 0.100
mm.sup.2, respectively ((2), (3), (4), (5));
biosensors 200 according to a modification of the first embodiment
shown in FIG. 2, wherein the number of the auxiliary sample supply
ports 14 is two (area: 0.003 mm.sup.2), two (area: 0.050 mm.sup.2),
four (area: 0.01 mm.sup.2), and nine (area: 0.01 mm.sup.2),
respectively ((6), (7), (8), (9));
a biosensor 300 according to another modification of the first
embodiment shown in FIG. 3, wherein the auxiliary sample supply
port 14 is rectangle in shape ((10));
a biosensor 500 according to the second embodiment shown in FIG. 5,
wherein the auxiliary sample supply ports 14 are formed on both the
first insulating substrate 1 and the second insulating substrate 8
((11));
a biosensor having an auxiliary sample supply port on the first
insulating substrate ((12));
a biosensor 600 according to the third embodiment shown in FIG. 6,
wherein the capillary 7 is Y-shaped ((13)); and
a biosensor 700 as a sensor for comparison shown in FIG. 7, wherein
a groove-shaped slit 15 is formed at a front end of a second
insulating substrate 8, and a sample supply port 13 and an
auxiliary sample supply port formed by the slit 15 are connected
((14)).
Then, 2 .mu.L of blood which is sufficient to completely fill the
sample supply port of the biosensor of this example is collected on
a fingertip, the finger is pressed against the sample supply port,
and the blood aspiration state when the sample supply port is
closed up is checked.
Table 1 shows the test results.
TABLE-US-00001 TABLE 1 area of number of AUX supply AUX supply
result sample port port 1 2 3 4 5 conventional sensor (1) -- 0 X X
X X X invention AUX supply port (2) 0.005 mm.sup.2 1 .DELTA.
.DELTA. X .DELTA. .largecircle. sensor on 2nd insulating (3) 0.010
mm.sup.2 1 .largecircle. .largecircle. .largecircle. .largecircle.
.large- circle. substrate (4) 0.030 mm.sup.2 1 .largecircle.
.largecircle. .largecircle. .largecircle. .large- circle. (5) 0.100
mm.sup.2 1 .largecircle. .largecircle. .largecircle. .largecircle.
.large- circle. (6) 0.003 mm.sup.2 2 .DELTA. .DELTA. X .DELTA.
.DELTA. (7) 0.05 mm.sup.2 2 .largecircle. .largecircle.
.largecircle. .largecircle. .large- circle. (8) 0.01 mm.sup.2 4
.largecircle. .largecircle. .largecircle. .largecircle. .large-
circle. (9) 0.01 mm.sup.2 9 .largecircle. .largecircle.
.largecircle. .largecircle. .large- circle. rectangular AUX (10)
0.01 mm.sup.2 1 .largecircle. .largecircle. .largecircle.
.largecircle. .large- circle. supply port (FIG. 3) AUX supply ports
(11) 0.01 mm.sup.2 2 .largecircle. .largecircle. .largecircle.
.largecircle. .large- circle. on both insulating substrates (FIG.
5) AUX supply port (12) 0.01 mm.sup.2 1 .largecircle. .largecircle.
.largecircle. .largecircle. .large- circle. on 1st insulating
substrate Y-shaped (13) 0.15 mm.sup.2 1 .largecircle. .largecircle.
.largecircle. .largecircle. .large- circle. capillary(FIG. 6)
comparison main supply port (14) 0.010 mm.sup.2 0 X X X .DELTA.
.DELTA. sensor short-circuited with AUX supply port (FIG. 7)
.largecircle.: Speedily and accurate aspiration is performed even
when finger is pressed. .DELTA.: Aspiration is lowered in speed or
stopped halfway when finger is pressed. X: Aspiration is stopped
when finger is pressed.
As is evident from Table 1, in the conventional biosensor having no
auxiliary sample supply port, when the finger is pressed against
the sample supply port, aspiration is stopped in all the results.
This is because the sample supply port is closed up by pressing an
elastic object such as a fingertip, and thereby supply of the
sample solution is prevented.
Further, when the area of the auxiliary sample supply port is 0.005
mm.sup.2, aspiration speed is lowered when the finger is pressed
against the supply port. It is estimated that the area of the
auxiliary sample supply port is small and insufficient to introduce
the blood into the capillary.
When the area of the auxiliary sample supply port is equal to or
larger than 0.01 mm.sup.2, speedily aspiration is carried out even
when the finger is pressed against the supply port. It is estimated
that even when the sample supply port is closed up and supply of
the sample solution is rate-limited, the sample solution is
speedily supplied from the auxiliary sample supply port.
When plural auxiliary sample supply ports are provided, the same
effects can be obtained so long as the total of the areas of the
supply ports is equal to or larger than 0.01 mm.sup.2.
In the case where the main supply port and the auxiliary supply
port are connected and a groove-shaped slit is formed at the front
end of the second insulating substrate as shown in FIG. 7,
aspiration is stopped or lowered in speed when the finger is
pressed against the main supply port, even though the area of the
groove is 0.01 mm.sup.2. It is estimated that when the sample
supply port and the auxiliary supply port are connected, the finger
pressed against the sample supply port undesirably adheres tightly
to the inside of the auxiliary supply port, and thereby the
auxiliary supply port becomes incapable of performing its
function.
On the other hand, favorable results can be obtained with respect
to the biosensor having a rectangle auxiliary sample supply port
(refer to FIG. 3), the biosensor having auxiliary sample supply
ports on both the first and second insulating substrates 1 and 2
(refer to FIG. 5), the biosensor having an auxiliary sample supply
port on the insulating substrate 1, and the biosensor having a
Y-shaped capillary (refer to FIG. 6).
When performing measurement with a very small quantity of sample
solution as in this example, if the sample supply port and the
auxiliary sample supply port are separated by 5 mm or more, it is
difficult to make the sample contact these ports simultaneously,
and favorable effects cannot be obtained.
Also when the area of the auxiliary sample supply port is equal to
or larger than 3 mm.sup.2, it is difficult to make the sample
contact the entirety of the auxiliary supply port for the same
reason as mentioned above, and the auxiliary supply port cannot
perform its function.
APPLICABILITY IN INDUSTRY
A biosensor according to the present invention is applicable to a
blood glucose sensor, a cholesterol sensor, a lactic acid sensor,
an alcohol sensor, an amino acid sensor, a fructose sensor, and a
sucrose sensor, which collect a very small quantity of sample
solution into a capillary and perform analysis. Further, samples
used for the analysis may include liquid samples such as blood,
urine, sweat, saliva, drinkable water, and sewage water.
* * * * *